Pest control agents are materials that limit the growth or spread of a living thing, such as by repelling, killing, preventing, or otherwise. Numerous pest control agents are known in the art, and many methods for introducing such a pest control agent into an environment also are known. For instance, the prior art has taught various repellents for pests such as rabbit, deer, dog, cat, squirrel, bird, mole, and mosquito. Repellents can broadly be defined as compositions that prevent, deter, or minimize pests from entering or remaining in target pest area. Repellents that are non-lethal at normally applied doses are available; in some cases, the same chemical used at low levels exhibits non-lethal repellency whereas use at higher levels is lethal. The prior art has also taught numerous pesticidal control agents and other types of control agents.
Many control agents take the form of oils, such as fragrant botanical oils. As one example, citronella oils are well known for efficacy in controlling mosquitoes by repelling mosquitoes from an area in which citronella oils are present. Botanical oils are advantageous for numerous reasons. Such oils are stable, are often strongly recognized by the target pest, and can be highly selective to the targeted pest. In some cases, even a few molecules of an appropriate agent can exhibit a strong response in the target pest while otherwise not affecting the local ecosystem.
Many commercially available botanical oils are formulated for delivery as aqueous sprays, which typically require employment of a hose-end sprayer for application. However, such liquid delivery systems are not desirable, because they are inefficient at controlling release of the volatile substances. Many botanical oils are expensive and available in limited quantities, and there is competition for such materials by for example, the food flavorings and fragrances industries. Accordingly, it is desirable to avoid waste and over-application of such oils.
Oils are generally liquid at the intended temperature of application. Although liquid oils are useful in many applications, in some case it is desirable to provide solid pest control formulations. Solid pest control products have a number of advantages in targeting an area for pest control. For instance, solid compositions often are more easily handled and applied then liquid compositions. For this reason, the prior art has provided numerous forms of solid pesticides and repellents, a familiar example of which is the citronella candle. In such cases, the majority of the solid pest control composition is composed of a carrier or sorbent material, the balance comprising the active ingredient. Generally, the active ingredient comprises a small percentage (less then about 10%) of the weight of the composition.
Certain plant-based sorbent materials have been proposed as carriers for use with pesticides and other control agents. For instance, materials such as corn cob, peanut hulls, starches, and the like have been proposed as carriers or pesticides for providing a solid control agent composition. Although such materials are useful and enjoy a number of advantages, in some respects the use of such materials suffers from certain drawbacks. For instance, when used with a lipophilic or oleolgenous control agent, the resulting composition can be oily to the touch. Additionally, when used with a fragrant repellent oil, such as citronella oil, the oil generally is released from the composition more rapidly than is often desired, thus necessitating more frequent application of the pest control composition. In many cases, it is desired to introduce the control agent into an environment in a sustained-release manner, by which is contemplated that at least some of the control agent is bound up with another material or otherwise is not immediately able to function in the environment for its intended purpose.
In some cases, particularly when the control agent comprises a botanical oil, it is desirable to provide a sorbent that allows sustained release of at least some of the control agent into an environment. U.S. patent application Ser. No. 10/172,588 and U.S. patent application Ser. No. 10/696,374, both assigned to Grain Processing Corporation of Muscatine, Iowa, contain excellent teachings as to pest control compositions, the compositions based, inter alia on corn germ or seed meal. As taught therein, a pest control composition, such a larvicide or the like, may be sorbed within a carrier. The carrier may comprise for instance, a spent corn germ sorbent. The resulting composition may be pelleted to form discrete plural particles. It has been observed that, while the foregoing compositions are suitable for use for a wide range of control agents (including botanical oils), for some oils the particles prepared in accordance with these teachings sometimes can feel oily to the touch.
The present invention seeks to provide a pest control composition that, in preferred embodiments, is in the form of discrete plural particles of a control agent sorbed within a carrier. In preferred embodiments, the invention seeks to provide a composition in the form of solid particles that are not substantially “oily” to the touch and that enable sustained-release of the control agent contained therewithin.